Arc time versus the time the job really takes
There are two clocks on every weld. Arc time is how long the arc is actually burning — length divided by travel speed. Job time is the wall-clock total once you add setup, tacking, repositioning, cleaning, and rest. The gap between them is the operator factor, and ignoring it is how shops underbid welding work.
The calculation
Arc time = (weld length x number of passes) / travel speed. Total job time = arc time / operator factor. An operator factor of 40 percent means the arc is on 40 percent of the clock, so a 10 minute arc job actually occupies about 25 minutes of a welders time.
Typical operator factors
| Situation | Operator factor |
|---|---|
| Hand welding, lots of repositioning | 20 – 30% |
| General fabrication | 30 – 45% |
| Long continuous seams | 45 – 60% |
| Mechanized / robotic | 60 – 90% |
Where this fits
The arc time here feeds two other tools: drop it into the welding gas calculator to size your shielding gas, and into the welding cost calculator to price labor.
Worked example
A 120 in weld at 12 IPM in a single pass is 10 minutes of arc time. At a 40 percent operator factor the job ties up about 25 minutes of labor — the number you should actually bill against.
FAQ
What travel speed should I use?
Use your measured bead speed for the process and position. MIG on plate often runs 10 to 20 IPM; out-of-position and root passes are slower. When unsure, time a known bead and divide its length by the seconds it took.
Why not just bill arc time?
Because nobody welds 60 minutes an hour. Tacking, grinding, fit-up, and moving the part are real labor. The operator factor turns honest arc time into honest job time.